Dropsondes--Work Horses in Hurricane Forecasting

Small cylinders dropped from airplanes gather atmospheric data on their way down

Inside a cylinder that is about the size of a roll of paper towels lives a circuit board filled with sensors. It's called a dropsonde, or "sonde" for short. It's a work horse of hurricane forecasting, dropping out of "Hurricane Hunter" airplanes right into raging storms. As the sonde falls through the air, its sensors gather data about the atmosphere to help us better understand climate and other atmospheric conditions.

"Dropsondes have a huge impact on our understanding of hurricanes and our ability to predict hurricanes," explains electrical engineer Terry Hock at the Earth Observing Laboratory in the National Center for Atmospheric Research (NCAR), located in Boulder, Colo.

With support from the National Science Foundation (NSF), Hock and his colleagues at NCAR have been designing, building and improving dropsonde technology for more than 30 years. "Our most current development is a fully automated dropsonde system for NASA's unmanned Global Hawk aircraft," says Hock.

Compared to earlier models, today's sondes are lighter weight, relatively inexpensive and loaded with sensors.

"We have a lot of electronics and, on the back side, a battery pack to operate the sonde. We have a temperature and two humidity sensors, and we have a GPS receiver," explains Hock, as he points out the different circuit board components. "As the sonde moves, we're using that GPS receiver to track the sonde's movements very precisely, which is then telling us the wind speed and wind direction. At the top of the sonde is a parachute which slows down the descent."

Electrical engineer Dean Lauritsen, a member of Hock's team, developed the system software on the aircraft, which controls the aircraft data system and process, and also displays dropsonde data during the sondes free fall to earth. There's such a system on the HIAPER, the NSF/NCAR Gulfstream V Research Aircraft, which uses sondes for scientific research, and a similar system used by the U.S. Air Force Reserve Hurricane Hunters in Biloxi, Miss., and the NOAA Hurricane Hunters in Tampa, Fla. On board each aircraft are a computer and a rack of electronic equipment to monitor and receive information from sondes. "The system is capable of tracking as many as eight dropsondes in the air at the same time. Each one of them is transmitting data on a separate frequency as it falls." says Lauritsen.

From the time the sonde leaves the aircraft, it is checking surroundings two times a second and sending information back to the aircraft, including pressure, temperature, humidity, wind speed, and wind direction. Future developments are expected to include sensors for chemicals such as ozone.

"We're taking vertical slices of the atmosphere constantly as the sonde falls," says Hock. "We're seeing very precise single measurements show up immediately on the computer screen."

Researchers process the information using NCAR-developed custom software, and then send it to weather forecasters and researchers around the world. In the case of the Hurricane Hunters, the information goes to the National Hurricane Center in Miami.

NCAR software engineer Charlie Martin develops custom software called ASPEN, which stands for Atmospheric Sounding Processing Environment. ASPEN helps make sense of all the dropsonde data. "Once the dropsonde has fallen through the atmosphere and the data has come back to the aircraft, that raw data needs a little more treatment before we send it to weather services around the world," explains Martin.

Martin points to a map showing a compilation of dropsonde wind data collected in August 2011, as Hurricane Irene was churning its way toward the Florida coast. "The winds are in a circular pattern," says Martin, as he identifies small triangles on the map that represent the wind and wind direction. "The center of the hurricane is clearly depicted in the center of the circular pattern. The National Hurricane Center uses this data along with other data to classify the hurricane and assign a category to it."

Hock and his team also custom fit aircraft with launchers to deploy the sondes, including one system for helium-filled balloons. In 2010, American and French researchers deployed balloons over Antarctica that dropped 600 sondes over a four-month period to study atmospheric conditions and the shifting ozone layer. "There is now a very dense set of measurements that came out of this project that has mapped the Antarctic atmosphere like it has never been done before," notes Martin.

"Atmospheric conditions above the Antarctic continent are hard to study since only a handful of sounding stations are regularly maintained there," says Peter Milne, program manager for ocean and atmospheric sciences within NSF's Office of Polar Programs. "Fortunately, the Antarctic polar vortex, a huge cyclone that sets up above the entire continent, is like the NASCAR of long distance ballooning, with balloons sweeping around the continent for as long as they stay aloft. Using these drifting platforms provided a unique data set."

Such "inside information" is helping scientists learn more about climate and hurricanes. Data from dropsondes is also giving scientists a better understanding about atmospheric conditions that spawn any number of weather conditions. Hock expects this will help forecasters make earlier and more precise hurricane predictions, giving people in the path of a killer storm more time to get out of harm's way.

Miles O'Brien, Science Nation Correspondent

Ann Kellan, Science Nation Producer

NASA's Global Hawk Investigating Atlantic Tropical Depression

NASA's Hurricane and Severe Storm Sentinel (HS3) airborne mission sent an unmanned Global Hawk aircraft this morning to study newborn Tropical Depression 14 in the central Atlantic Ocean that seems primed for further development. The Global Hawk left NASA's Wallops Flight Facility on Wallops Island, Va., this morning for a planned 26-hour flight to investigate the depression.

NASA's latest hurricane science field campaign began on Sept. 7 when the Global Hawk flew over Hurricane Leslie in the Atlantic Ocean. HS3 marks the first time NASA is flying Global Hawks from the U.S. East Coast.

According to Chris Naftel, project manager of NASA's Global Hawk program at NASA's Dryden Flight Research Center, Edwards Air Base, Calif., the Global Hawk aircraft took off at 7:06 a.m. EDT and headed for Tropical Depression 14, which at the time of take-off, was still a developing low pressure area called System 91L.

At 1500 UTC (11 a.m. EDT), Tropical Depression 14 was located near 16.3 North latitude and 43.1 West longitude, about 1,210 miles (1,950 km) east of the Lesser Antilles. The depression had maximum sustained winds near 35 mph. It was moving to the west near 10 mph (17 kmh) and had a minimum central pressure of 1006 millibars.

The National Hurricane Center expects Tropical Depression 14 to strengthen into a tropical storm over the next 48 hours, and turn to the northwest.

On Sept. 10, the Tropical Rainfall Measuring Mission (TRMM) satellite passed over Tropical Depression 14, when it was known as low pressure System 91L and data from TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) were used to create a rainfall analysis. The data was overlaid on a combination infrared and visible image from TRMM's Visible and InfraRed Scanner (VIRS) and showed that System 91L was getting organized and that convective storms reaching heights of about 13km (~8.1 miles) were dropping heavy rain to the northwest and northeast of the center of the circulation.

The HS3 mission targets the processes that underlie hurricane formation and intensity change. The data collected will help scientists decipher the relative roles of the large-scale environment and internal storm processes that shape these systems.

HS3 is supported by several NASA centers including Wallops; Goddard; Dryden; Ames Research Center, Moffett Field, Calif.; Marshall Space Flight Center, Huntsville, Ala.; and the Jet Propulsion Laboratory, Pasadena, Calif. HS3 also has collaborations with partners from government agencies and academia.

HS3 is an Earth Venture mission funded by NASA's Science Mission Directorate in Washington. Earth Venture missions are managed by NASA's Earth System Science Pathfinder Program at the agency's Langley Research Center in Hampton, Va. The HS3 mission is managed by the Earth Science Project Office at NASA's Ames Research Center.

Rob Gutro

NASA's Goddard Space Flight Center, Greenbelt, Md.

Manmade "Wall of Wind" Creates Hurricane Force Winds to Test Construction

Manufacturers learn quickly if their products could withstand the real thing

A Category 5 hurricane is a monster of a storm that most people would want to avoid. But, civil engineer Arindam Chowdhury actually recreates those monster hurricane force winds in hopes of helping people better prepare for the real thing.

With support from the National Science Foundation (NSF), Chowdhury and his team at Florida International University (FIU) and the International Hurricane Research Center designed a 15-foot-tall "Wall of Wind," aptly nicknamed WOW. The wall is made up of 12 giant fans, which can create the intensity of a Category 5 hurricane with 157-mph winds if the fans are running at full blast.

The goal is to see if low rise structures and building materials can withstand the same wind forces the structures and materials would face in a full-blown hurricane. "Based on our testing of rooftop equipment, such as AC units on building roofs, we made recommendations that are now in the Florida Building Code," says Chowdhury.

"Our long-term goal is to prevent hazardous wind from becoming a disaster," says Kishor Mehta, program director for hazard mitigation and structural engineering within NSF's Engineering Directorate. "This facility enables engineers to collect precise measurements of wind interacting with buildings, in addition to the visible evidence of the vulnerability of building materials exposed to hurricane force winds. This combination of basic research and visual evidence will lead to safer, more cost effective construction."

Manufacturers come to FIU to put some of their products to the test. During one test, researchers attach a solar panel manufactured by Power Panel Inc. to the roof of a small building. The building is secured on a rotating turntable directly in front of WOW. The turntable allows researchers to rotate the structure and expose the solar panel to wind from all directions.

In a nearby trailer, researchers huddle around computers at an informal control center. With the click of a mouse, they crank up the fans to create a fake hurricane. "I'm going to go up to 60 mph," says the researcher who is at the controls. He uses a walkie talkie to warn his team members who are outside preparing the building and the solar panel. Hearing that, they move out of the way as the fans start to blow.

Rob Kornahrens, part owner of Power Panel Inc., sits in the control room glued to a monitor as the test gets underway. Fan speed is increased to 90 mph. "We want to make sure the glass insert stays within the frame," says Kornahrens. "Second thing we're looking for is that the whole unit stays on the racking itself. Third thing is the attachment of the racking to the building. We want to make sure that doesn't come off the structure."

So far, so good, and the fans are now blowing at 120 mph. The building is swaying. The solar panel is staying on the roof. Sensors on the building measure the pressures on the panels. Satisfied with this first round, Kornahrens asks: "Can we flip it around?" Researchers shut off the fans and rotate the turntable to expose another side of the panel to head winds.

"Now we can see the effect of the wind and get the data from all the directions," explains Chowdhury.

"I don't think we'll see any damage to the panel based on what I saw," says Kornahrens. He is pleased with the results and with the test itself. "This is great. You can't get this in any other kind of test!"

Next up, testing roof tiles and a new adhesive tile foam. "That foam really works with this good tile," says Manny Oyola with Eagle Roofing Products. He is with his supplier Riku Ylipelkonen of 3M, the company that manufactures polyfoam roof tile adhesive. They, along with another roofing company owner, Tim Graboski, stand in the control room and watch WOW's forces on the roof tiles and foam.

The fans start to whirl, blowing 90, then 120, and finally 140 mph. The tiles and foam stay firmly on the roof and they pass with flying colors. But, does the building itself? Not so much. The entire structure lets loose from its foundation and flies off the turntable crashing in a nearby field. "It's a powerful machine," Chowdhury smiles, "even more powerful than I thought." On a serious note, Chowdhury says such foundation failures are rare.

Lessons learned on building materials and structures tested at WOW could help improve design and even save lives.

"The thing we feel good about is that 2012 is the 20th anniversary of Hurricane Andrew, the Category 5 hurricane that devastated south Florida, including Homestead," adds Chowdhury. "Today, we can simulate the hurricane strength of Andrew, learn from the tests and make changes to mitigate damages." Now, that's a WOW!

The research in this episode was funded by NSF through the American Recovery and Reinvestment Act of 2009.

Miles O'Brien, Science Nation Correspondent

Ann Kellan, Science Nation Producer

Tornadoes -- Science Behind the News

Tornadoes are violent, twisting columns of air with wind speeds over 100 miles per hour that can tear communities apart. Josh Wurman, an atmospheric scientist, explains that tornadoes develop in a special type of thunderstorm called a supercell, but says there are still mysteries to unravel.

Credit: NBC Learn and the National Science Foundation

NASA Voyage Set To Explore Link Between Sea Saltiness And Climate

Steve Cole

Headquarters, Washington          

202-358-0918

stephen.e.cole@nasa.gov

 

WASHINGTON -- A NASA-sponsored expedition is set to sail to the North Atlantic's saltiest spot to get a detailed, 3-D picture of how salt content fluctuates in the ocean's upper layers and how these variations are related to shifts in rainfall patterns around the planet.

The research voyage is part of a multi-year mission, dubbed the Salinity Processes in the Upper Ocean Regional Study (SPURS), which will deploy multiple instruments in different regions of the ocean. The new data also will help calibrate the salinity measurements NASA's Aquarius instrument has been collecting from space since August 2011.

SPURS scientists aboard the research vessel Knorr leave Sept. 6 from the Woods Hole Oceanographic Institution in Woods Hole, Mass., and head toward a spot known as the Atlantic surface salinity maximum, located halfway between the Bahamas and the western coast of North Africa. The expedition also is supported by the National Oceanic and Atmospheric Administration and the National Science Foundation.

The researchers will spend about three weeks on site deploying instruments and taking salinity, temperature and other measurements, before sailing to the Azores to complete the voyage on Oct. 9.

They will return with new data to aid in understanding one of the most worrisome effects of climate change -- the acceleration of Earth's water cycle. As global temperatures go up, evaporation increases, altering the frequency, strength, and distribution of rainfall around the planet, with far-reaching implications for life on Earth.

"What if the drought in the U.S. Midwest became permanent? To understand whether that could happen we must understand the water cycle and how it will change as the climate continues to warm," said Raymond Schmitt, a physical oceanographer at Woods Hole and principal investigator for SPURS. "Getting that right is going to involve understanding the ocean, because the ocean is the source of most of the water."

Oceanographers believe the ocean retains a better record of changes in precipitation than land, and translates these changes into variations in the salt concentration of its surface waters. Scientists studying the salinity records of the past 50 years say they already see the footprint of an increase in the speed of the water cycle. The places in the ocean where evaporation has increased and rain has become scarcer have turned saltier over time, while the spots that now receive more rain have become fresher. This acceleration ultimately may exacerbate droughts and floods around the planet. Some climate models, however, predict less dramatic changes in the global water cycle.

"With SPURS we hope to find out why these climate models do not track our observations of changing salinities," said Eric Lindstrom, physical oceanography program scientist at NASA Headquarters in Washington. "We will investigate to what extent the observed salinity trends are a signature of a change in evaporation and precipitation over the ocean versus the ocean's own processes, such as the mixing of salty surface waters with deeper and fresher waters or the sideways transport of salt."

To learn more about what drives salinity, the SPURS researchers will deploy an array of instruments and platforms, including autonomous gliders, sensor-laden buoys and unmanned underwater vehicles. Some will be collected before the research vessel heads to the Azores, but others will remain in place for a year or more, providing scientists with data on seasonal variations of salinity.

Some of the devices used during SPURS to explore the Atlantic's saltiest spot will focus on the outer edges of the study area, traveling for hundreds of miles and studying the broadest salinity features. Other instruments will explore smaller areas nested inside the research site, focusing on smaller fluxes of salt in the waters. The suite of ocean instruments will complement data from NASA's salinity-sensing instrument aboard the Aquarius/SAC-D (Satelite de Aplicaciones Cientificas-D) observatory, and be integrated into real-time computer models that will help guide researchers to the most interesting phenomena in the cruise area.

"We'll be able to look at lots of different scales of salinity variability in the ocean, some of which can be seen from space, from a sensor like Aquarius," said David Fratantoni, a physical oceanographer with Woods Hole and a member of the SPURS expedition. "But we're also trying to see variations in the ocean that can't be resolved by current satellite technology."

The 2012 SPURS measurements in the North Atlantic will help scientists understand the behavior of other high-salinity regions around the world. A second SPURS expedition in 2015 will investigate low-salinity regions where there is a high input of fresh water, such as the mouth of a large river or the rainy belts near the equator.

For more information on the SPURS expedition, visit http://spurs.jpl.nasa.gov/SPURS.

For more information on Aquarius, visit http://www.nasa.gov/aquarius.

Regular blog updates from the SPURS expedition will be posted at

http://go.nasa.gov/PuyO5q.

- end -